Ophthalmic instruments often include a chin and forehead rest to stabilise a subject's head during an examination or procedure on the subject eye. Typical ophthalmic instruments that are mounted on a base and have a chin-rest assembly include retinal or fundus cameras, slit lamps and tonometers.
It is sometimes required that the ophthalmic instrument is transported to a different area to provide a service. When transporting an ophthalmic instrument which has a chin-rest and base that do not fold, a case large enough to fit the instrument is required. The size of the instrument is typically defined by the necessary size of the base to allow movement of the moveable instrument optics head sideways to view both subject eyes whilst remaining stable, and a protruding chin-rest to support the subject's head while sitting upright with the instrument base resting on a conventional table. As a result the transport case for the non-folding ophthalmic instrument is typically too large to be carried on commercial airline flights as standard check-in luggage, and certainly too large to carry on-board as personal luggage.
Some manufacturers have addressed this problem by allowing the chin-rest and base to be detached from the instrument so that the various components can be packaged more compactly for transport. Although effective, this is not convenient for the user as disassembly and packing of separate components is required. The width of the base and chinrest may still be larger than necessary as the base width has to be sufficient to prevent the instrument falling over when the moveable optics head is moved sideways. Removable or folding supports may be provided to maintain the stability of the instrument in this situation, but there is a risk that the instrument may fall over if the support is not properly in place when the moveable optics head is moved sideways.
It is desirable that an arrangement for folding the base and chin-rest of an ophthalmic instrument without separation be provided that allows the instrument dimensions to be reduced to a size that is suitable for carrying on-board commercial airline flights or for transport in a padded carry case that is small enough to be checked in as standard baggage. A reduction in size of the ophthalmic instrument also improves portability for general transport and manual carrying. It is also desirable that the folding arrangement does not require tools, and is such that the system does not have to be unfolded or assembled in a particular order to avoid an unstable configuration existing.
A previous design by this inventor comprised a chinrest assembly that slid upwards and rotated into normal working position and a support arm that folded out horizontally to provide the necessary stability. This system was effective, but the folded instrument was less compact than required, the folding action was complex and not entirely intuitive. After much experimentation a different arrangement was devised that is the subject of this patent application.